To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands or 28 GHz bands or 38 Ghz bands, so as to accomplish higher data rates by utilizing the vast bandwidth available in these mmWave bands. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed and proposed to be used in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.
In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
In a general cellular system, measurement samples are acquired during a predetermined period to exclude a shadow effect and a short-term fading effect, and then an average is calculated. Thereafter, in order to determine whether a predetermined event is satisfied, the average is compared with a preset threshold. For example, it is assumed that a measurement report is performed when a simple event, such as a measurement average of a serving cell equal to or smaller than a threshold, is configured. A User Equipment (UE) measures a configured measurement value to perform a proper average calculation process, and then compares whether the measured average of the serving cell is equal to or smaller than a preset threshold on every measurement period. When the measurement value of the serving cell is equal to or smaller than the preset threshold, the UE transmits a measurement report to an evolved NodeB (eNB). Based on the measurement report, the eNB may perform appropriate tasks such as allowing the UE to measure cells in frequencies different from that of the measurement cell of the current UE.
FIG. 1 illustrates a process for generally performing a measurement report procedure according to each layer. Referring to FIG. 1, layer 1 (physical layer) performs measurement at for eg. every 40 ms, calculates an average of values measured in every 200 ms, and reports the calculated average to layer 3. This is a general measurement result report procedure in the LTE system. Layer 3 compares a preset threshold and the reported average. Layer 3 performs a process of calculating an average of different times according to an averaging parameter set to calculate the final filtered value, which when a final filtered value meets the preset threshold triggers reporting of the measured value.
Alternatively, the same average value calculation process may be used. When the periodic measurement value report is configured, measurement values may be reported to the eNB.
A general layer 3 average calculation in LTE is performed based on an equation of (1−a)*Fn−1+a*Mn. In the equation, a denotes a filter coefficient, Mn denotes an nth layer 1 average, and Fn−1 denotes an n−1th layer 3 average.
Various events, which can be configured in the LTE system, are shown in the below table.
Event3GPP TS 36.331A1Serving > ThresholdA2Serving > ThresholdA3Neighbor > Pcell + OffsetA4Neighbor > ThresholdA5Pcell < ThresholdNeighbor > Threshold 2A6Neighbor > Scell + Offset
Cells, which meet a reference for reporting (meet preset thresholds) are arranged and reported in a descending order of measurement values later. A reporting configuration may be configured as the maximum number of cells, to which the report can be provided (for example, a general value is 8).
Measurement values in LTE may be received signal received power (RSRP) or received signal received quality (RSRQ).
Meanwhile, in a cellular system based on the millimeter wave, it is required to overcome a high propagation loss in order to actually operate the cellular communication system, so that beamforming is needed. For example, in order to operate a cellular system based on millimeter wave band up to a range of 200 meters, a beam width of about 10 degrees is required.
Further, the beamforming requires a method of measuring each beam, reporting a measurement result, and using the measurement result for selection of the best beam(s) for communication with the base station.